The invention relates to methods and apparatus for metal casting, and more particularly to methods and apparatus for casting a two cycle cylinder block in a lost foam casting process. Even more particularly, the invention relates to foam patterns and methods for making foam patterns for casting a two cycle cylinder block in a lost foam casting process.
The casting of two cycle cylinder blocks has always been difficult, due to the many interior ports and passages. For example, a typical two cycle cylinder block includes a cylinder bore, an exhaust port and an inlet port communicating with the cylinder bore, an exhaust passage communicating with the exhaust port, a transfer passage communicating with the inlet port, and a water cooling passage. A loop scavenged cylinder block includes at least two inlet ports and transfer passages. Because of the complicated construction of two cycle cylinder blocks, complicated casting techniques have been required.
Lost foam casting uses a foam pattern having structure identical to the structure of the object to be cast. Foam patterns are typically fabricated by injection molding, and it can be appreciated by one skilled in the injection molding art that molding a foam pattern having the structure of a two cycle cylinder block would be a difficult task.
It is known in the lost foam casting art to form a foam pattern by gluing various pieces of a pattern together.
Attention is directed to the following United States patents which relate to casting with consumable patterns into casting of engine parts:
______________________________________ Trumbauer 4,093,018 June 6, 1978 Hale 4,328,770 May 11, 1982 Trumbauer 4,462,453 July 31, 1984 Woolcott 3,459,253 August 5, 1969 Kearney 4,190,093 February 26, 1980 Ernest 4,197,899 April 15, 1980 ______________________________________